WO-A-2008082511 discloses a process where two or more polymerization reactors feed one high-pressure separator. The pressure in the high-pressure separator can be up to 25 MPa. WO-A-2008109094 discloses a process for recovering volatile components from polymer solution. The liquid-liquid separation process (LOST phase separation) returns the volatile components to the polymerization reactors optionally via one or more separation towers. U.S. Pat. No. 2,691,674 discloses a solution polymerization process with two-step recovery of volatile hydrocarbons from the polymer solution.
WO-A-2011087728, U.S. Pat. No. 8,916,659 B1 and WO-A-0234795 all disclose processes in which the solution of one or more solution polymerization reactors is separated in a liquid-liquid high pressure separator. In a further downstream separation stage the polymer-enriched liquid stream is fed into a vapour-liquid low pressure separator in which remaining volatile compounds are separated from the polymer-enriched liquid stream. The vapour stream containing the volatile compounds is then passed to a purification tower which essentially is a distillation column for separating the highly volatile compounds from the heavier less volatile compounds of the vapour stream.
There is still the need for an efficient process for withdrawing polyolefins from a solution polymerization reactor.